Auto merge of #48985 - scalexm:lowering, r=nikomatsakis

MVP for chalkification

r? @nikomatsakis

src/librustc/dep_graph/dep_node.rs

@@ -648,6 +648,8 @@ define_dep_nodes!( <'tcx>
     [] GetSymbolExportLevel(DefId),
 
     [input] Features,
+
+    [] ProgramClausesFor(DefId),
 );
 
 trait DepNodeParams<'a, 'gcx: 'tcx + 'a, 'tcx: 'a> : fmt::Debug {

src/librustc/ich/impls_ty.rs

@@ -1285,3 +1285,86 @@ impl_stable_hash_for!(struct infer::canonical::QueryRegionConstraints<'tcx> {
 impl_stable_hash_for!(enum infer::canonical::Certainty {
     Proven, Ambiguous
 });
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for traits::WhereClauseAtom<'tcx> {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        use traits::WhereClauseAtom::*;
+
+        mem::discriminant(self).hash_stable(hcx, hasher);
+        match self {
+            Implemented(trait_ref) => trait_ref.hash_stable(hcx, hasher),
+            ProjectionEq(projection) => projection.hash_stable(hcx, hasher),
+        }
+    }
+}
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for traits::DomainGoal<'tcx> {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        use traits::DomainGoal::*;
+
+        mem::discriminant(self).hash_stable(hcx, hasher);
+        match self {
+            Holds(where_clause) |
+            WellFormed(where_clause) |
+            FromEnv(where_clause) => where_clause.hash_stable(hcx, hasher),
+
+            WellFormedTy(ty) => ty.hash_stable(hcx, hasher),
+            FromEnvTy(ty) => ty.hash_stable(hcx, hasher),
+            RegionOutlives(predicate) => predicate.hash_stable(hcx, hasher),
+            TypeOutlives(predicate) => predicate.hash_stable(hcx, hasher),
+        }
+    }
+}
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for traits::Goal<'tcx> {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        use traits::Goal::*;
+
+        mem::discriminant(self).hash_stable(hcx, hasher);
+        match self {
+            Implies(hypotheses, goal) => {
+                hypotheses.hash_stable(hcx, hasher);
+                goal.hash_stable(hcx, hasher);
+            },
+            And(goal1, goal2) => {
+                goal1.hash_stable(hcx, hasher);
+                goal2.hash_stable(hcx, hasher);
+            }
+            Not(goal) => goal.hash_stable(hcx, hasher),
+            DomainGoal(domain_goal) => domain_goal.hash_stable(hcx, hasher),
+            Quantified(quantifier, goal) => {
+                quantifier.hash_stable(hcx, hasher);
+                goal.hash_stable(hcx, hasher);
+            },
+        }
+    }
+}
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for traits::Clause<'tcx> {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        use traits::Clause::*;
+
+        mem::discriminant(self).hash_stable(hcx, hasher);
+        match self {
+            Implies(hypotheses, goal) => {
+                hypotheses.hash_stable(hcx, hasher);
+                goal.hash_stable(hcx, hasher);
+            }
+            DomainGoal(domain_goal) => domain_goal.hash_stable(hcx, hasher),
+            ForAll(clause) => clause.hash_stable(hcx, hasher),
+        }
+    }
+}
+
+impl_stable_hash_for!(enum traits::QuantifierKind {
+    Universal,
+    Existential
+});

src/librustc/traits/mod.rs

@@ -29,6 +29,7 @@ use infer::{InferCtxt};
 
 use rustc_data_structures::sync::Lrc;
 use std::rc::Rc;
+use std::convert::From;
 use syntax::ast;
 use syntax_pos::{Span, DUMMY_SP};
 
@@ -244,6 +245,69 @@ pub type Obligations<'tcx, O> = Vec<Obligation<'tcx, O>>;
 pub type PredicateObligations<'tcx> = Vec<PredicateObligation<'tcx>>;
 pub type TraitObligations<'tcx> = Vec<TraitObligation<'tcx>>;
 
+/// The following types:
+/// * `WhereClauseAtom`
+/// * `DomainGoal`
+/// * `Goal`
+/// * `Clause`
+/// are used for representing the trait system in the form of
+/// logic programming clauses. They are part of the interface
+/// for the chalk SLG solver.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub enum WhereClauseAtom<'tcx> {
+    Implemented(ty::TraitPredicate<'tcx>),
+    ProjectionEq(ty::ProjectionPredicate<'tcx>),
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub enum DomainGoal<'tcx> {
+    Holds(WhereClauseAtom<'tcx>),
+    WellFormed(WhereClauseAtom<'tcx>),
+    FromEnv(WhereClauseAtom<'tcx>),
+    WellFormedTy(Ty<'tcx>),
+    FromEnvTy(Ty<'tcx>),
+    RegionOutlives(ty::RegionOutlivesPredicate<'tcx>),
+    TypeOutlives(ty::TypeOutlivesPredicate<'tcx>),
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub enum QuantifierKind {
+    Universal,
+    Existential,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum Goal<'tcx> {
+    // FIXME: use interned refs instead of `Box`
+    Implies(Vec<Clause<'tcx>>, Box<Goal<'tcx>>),
+    And(Box<Goal<'tcx>>, Box<Goal<'tcx>>),
+    Not(Box<Goal<'tcx>>),
+    DomainGoal(DomainGoal<'tcx>),
+    Quantified(QuantifierKind, Box<ty::Binder<Goal<'tcx>>>)
+}
+
+impl<'tcx> From<DomainGoal<'tcx>> for Goal<'tcx> {
+    fn from(domain_goal: DomainGoal<'tcx>) -> Self {
+        Goal::DomainGoal(domain_goal)
+    }
+}
+
+impl<'tcx> From<DomainGoal<'tcx>> for Clause<'tcx> {
+    fn from(domain_goal: DomainGoal<'tcx>) -> Self {
+        Clause::DomainGoal(domain_goal)
+    }
+}
+
+/// This matches the definition from Page 7 of "A Proof Procedure for the Logic of Hereditary
+/// Harrop Formulas".
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum Clause<'tcx> {
+    // FIXME: again, use interned refs instead of `Box`
+    Implies(Vec<Goal<'tcx>>, DomainGoal<'tcx>),
+    DomainGoal(DomainGoal<'tcx>),
+    ForAll(Box<ty::Binder<Clause<'tcx>>>),
+}
+
 pub type Selection<'tcx> = Vtable<'tcx, PredicateObligation<'tcx>>;
 
 #[derive(Clone,Debug)]

src/librustc/traits/structural_impls.rs

@@ -425,3 +425,138 @@ BraceStructTypeFoldableImpl! {
         obligations
     } where T: TypeFoldable<'tcx>
 }
+
+impl<'tcx> fmt::Display for traits::WhereClauseAtom<'tcx> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        use traits::WhereClauseAtom::*;
+
+        match self {
+            Implemented(trait_ref) => write!(fmt, "Implemented({})", trait_ref),
+            ProjectionEq(projection) => write!(fmt, "ProjectionEq({})", projection),
+        }
+    }
+}
+
+impl<'tcx> fmt::Display for traits::DomainGoal<'tcx> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        use traits::DomainGoal::*;
+        use traits::WhereClauseAtom::*;
+
+        match self {
+            Holds(wc) => write!(fmt, "{}", wc),
+            WellFormed(Implemented(trait_ref)) => write!(fmt, "WellFormed({})", trait_ref),
+            WellFormed(ProjectionEq(projection)) => write!(fmt, "WellFormed({})", projection),
+            FromEnv(Implemented(trait_ref)) => write!(fmt, "FromEnv({})", trait_ref),
+            FromEnv(ProjectionEq(projection)) => write!(fmt, "FromEnv({})", projection),
+            WellFormedTy(ty) => write!(fmt, "WellFormed({})", ty),
+            FromEnvTy(ty) => write!(fmt, "FromEnv({})", ty),
+            RegionOutlives(predicate) => write!(fmt, "RegionOutlives({})", predicate),
+            TypeOutlives(predicate) => write!(fmt, "TypeOutlives({})", predicate),
+        }
+    }
+}
+
+impl fmt::Display for traits::QuantifierKind {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        use traits::QuantifierKind::*;
+
+        match self {
+            Universal => write!(fmt, "forall"),
+            Existential => write!(fmt, "exists"),
+        }
+    }
+}
+
+impl<'tcx> fmt::Display for traits::Goal<'tcx> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        use traits::Goal::*;
+
+        match self {
+            Implies(hypotheses, goal) => {
+                write!(fmt, "if (")?;
+                for (index, hyp) in hypotheses.iter().enumerate() {
+                    if index > 0 {
+                        write!(fmt, ", ")?;
+                    }
+                    write!(fmt, "{}", hyp)?;
+                }
+                write!(fmt, ") {{ {} }}", goal)
+            }
+            And(goal1, goal2) => write!(fmt, "({} && {})", goal1, goal2),
+            Not(goal) => write!(fmt, "not {{ {} }}", goal),
+            DomainGoal(goal) => write!(fmt, "{}", goal),
+            Quantified(qkind, goal) => {
+                // FIXME: appropriate binder names
+                write!(fmt, "{}<> {{ {} }}", qkind, goal.skip_binder())
+            }
+        }
+    }
+}
+
+impl<'tcx> fmt::Display for traits::Clause<'tcx> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        use traits::Clause::*;
+
+        match self {
+            Implies(hypotheses, goal) => {
+                write!(fmt, "{}", goal)?;
+                if !hypotheses.is_empty() {
+                    write!(fmt, " :- ")?;
+                    for (index, condition) in hypotheses.iter().enumerate() {
+                        if index > 0 {
+                            write!(fmt, ", ")?;
+                        }
+                        write!(fmt, "{}", condition)?;
+                    }
+                }
+                write!(fmt, ".")
+            }
+            DomainGoal(domain_goal) => write!(fmt, "{}.", domain_goal),
+            ForAll(clause) => {
+                // FIXME: appropriate binder names
+                write!(fmt, "forall<> {{ {} }}", clause.skip_binder())
+            }
+        }
+    }
+}
+
+EnumTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for traits::WhereClauseAtom<'tcx> {
+        (traits::WhereClauseAtom::Implemented)(trait_ref),
+        (traits::WhereClauseAtom::ProjectionEq)(projection),
+    }
+}
+
+EnumTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for traits::DomainGoal<'tcx> {
+        (traits::DomainGoal::Holds)(wc),
+        (traits::DomainGoal::WellFormed)(wc),
+        (traits::DomainGoal::FromEnv)(wc),
+        (traits::DomainGoal::WellFormedTy)(ty),
+        (traits::DomainGoal::FromEnvTy)(ty),
+        (traits::DomainGoal::RegionOutlives)(predicate),
+        (traits::DomainGoal::TypeOutlives)(predicate),
+    }
+}
+
+CloneTypeFoldableImpls! {
+    traits::QuantifierKind,
+}
+
+EnumTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for traits::Goal<'tcx> {
+        (traits::Goal::Implies)(hypotheses, goal),
+        (traits::Goal::And)(goal1, goal2),
+        (traits::Goal::Not)(goal),
+        (traits::Goal::DomainGoal)(domain_goal),
+        (traits::Goal::Quantified)(qkind, goal),
+    }
+}
+
+EnumTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for traits::Clause<'tcx> {
+        (traits::Clause::Implies)(hypotheses, goal),
+        (traits::Clause::DomainGoal)(domain_goal),
+        (traits::Clause::ForAll)(clause),
+    }
+}

src/librustc/ty/maps/config.rs

@@ -693,6 +693,12 @@ impl<'tcx> QueryDescription<'tcx> for queries::generics_of<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription<'tcx> for queries::program_clauses_for<'tcx> {
+    fn describe(_tcx: TyCtxt, _: DefId) -> String {
+        format!("generating chalk-style clauses")
+    }
+}
+
 macro_rules! impl_disk_cacheable_query(
     ($query_name:ident, |$key:tt| $cond:expr) => {
         impl<'tcx> QueryDescription<'tcx> for queries::$query_name<'tcx> {

src/librustc/ty/maps/mod.rs

@@ -38,6 +38,7 @@ use traits::query::{CanonicalProjectionGoal, CanonicalTyGoal, NoSolution};
 use traits::query::dropck_outlives::{DtorckConstraint, DropckOutlivesResult};
 use traits::query::normalize::NormalizationResult;
 use traits::specialization_graph;
+use traits::Clause;
 use ty::{self, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt};
 use ty::steal::Steal;
 use ty::subst::Substs;
@@ -417,6 +418,8 @@ define_maps! { <'tcx>
         -> usize,
 
     [] fn features_query: features_node(CrateNum) -> Lrc<feature_gate::Features>,
+
+    [] fn program_clauses_for: ProgramClausesFor(DefId) -> Lrc<Vec<Clause<'tcx>>>,
 }
 
 //////////////////////////////////////////////////////////////////////

src/librustc/ty/maps/plumbing.rs

@@ -935,6 +935,8 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
 
         DepKind::GetSymbolExportLevel => { force!(symbol_export_level, def_id!()); }
         DepKind::Features => { force!(features_query, LOCAL_CRATE); }
+
+        DepKind::ProgramClausesFor => { force!(program_clauses_for, def_id!()); }
     }
 
     true

src/librustc/ty/mod.rs

@@ -1073,9 +1073,12 @@ impl<'tcx> PolyTraitPredicate<'tcx> {
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct OutlivesPredicate<A,B>(pub A, pub B); // `A : B`
 pub type PolyOutlivesPredicate<A,B> = ty::Binder<OutlivesPredicate<A,B>>;
-pub type PolyRegionOutlivesPredicate<'tcx> = PolyOutlivesPredicate<ty::Region<'tcx>,
-                                                                   ty::Region<'tcx>>;
-pub type PolyTypeOutlivesPredicate<'tcx> = PolyOutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
+pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>,
+                                                           ty::Region<'tcx>>;
+pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>,
+                                                         ty::Region<'tcx>>;
+pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<RegionOutlivesPredicate<'tcx>>;
+pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<TypeOutlivesPredicate<'tcx>>;
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct SubtypePredicate<'tcx> {

src/librustc_driver/driver.rs

@@ -1091,6 +1091,10 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(trans: &TransCrate,
 
         time(sess, "lint checking", || lint::check_crate(tcx));
 
+        time(sess,
+             "dumping chalk-like clauses",
+             || rustc_traits::lowering::dump_program_clauses(tcx));
+
         return Ok(f(tcx, analysis, rx, tcx.sess.compile_status()));
     })
 }

src/librustc_traits/lib.rs

@@ -29,6 +29,7 @@ mod dropck_outlives;
 mod normalize_projection_ty;
 mod normalize_erasing_regions;
 mod util;
+pub mod lowering;
 
 use rustc::ty::maps::Providers;
 
@@ -39,6 +40,7 @@ pub fn provide(p: &mut Providers) {
         normalize_projection_ty: normalize_projection_ty::normalize_projection_ty,
         normalize_ty_after_erasing_regions:
             normalize_erasing_regions::normalize_ty_after_erasing_regions,
+        program_clauses_for: lowering::program_clauses_for,
         ..*p
     };
 }